Basso Enzo, Horstmann Johannes, Rakhimberdiev Eldar, Abad-Gómez José M, Masero José A, Gutiérrez Jorge S, Valenzuela Jorge, Ruiz Jorge, Navedo Juan G
Bird Ecology Lab, Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, Valdivia, Chile.
Programa de Doctorado en Ecología y Evolución, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
Mov Ecol. 2023 Sep 1;11(1):55. doi: 10.1186/s40462-023-00411-3.
Long-distance migratory birds spend most of their annual cycle in non-breeding areas. During this period birds must meet their daily nutritional needs and acquire additional energy intake to deal with future events of the annual cycle. Therefore, patterns of space use and movement may emerge as an efficient strategy to maintain a trade-off between acquisition and conservation of energy during the non-breeding season. However, there is still a paucity of research addressing this issue, especially in trans-hemispheric migratory birds.
Using GPS-tracking data and a recently developed continuous-time stochastic process modeling framework, we analyzed fine-scale movements in a non-breeding population of Hudsonian godwits (Limosa haemastica), a gregarious long-distance migratory shorebird. Specifically, we evaluated if these extreme migrants exhibit restricted, shared, and periodic patterns of space use on one of their main non-breeding grounds in southern South America. Finally, via a generalized additive model, we tested if the observed patterns were consistent within a circadian cycle.
Overall, godwits showed finely-tuned range-residence and periodic movements (each 24-72 h), being similar between day and night. Remarkably, range-resident individuals segregated spatially into three groups. In contrast, a smaller fraction of godwits displayed unpredictable and irregular movements, adding functional connectivity within the population.
In coastal non-breeding areas where resource availability is highly predictable due to tidal cycles, range-resident strategies during both the day and night are the common pattern in a long-distance shorebird population. Alternative patterns exhibited by a fraction of non-resident godwits provide functional connectivity and suggest that the exploratory tendency may be essential for information acquisition and associated with individual traits. The methodological approach we have used contributes to elucidate how the composition of movement phases operates during the non-breeding season in migratory species and can be replicated in non-migratory species as well. Finally, our results highlight the importance of considering movement as a continuum within the annual cycle.
长途候鸟在其年度周期的大部分时间都处于非繁殖区。在此期间，鸟类必须满足其每日营养需求，并获取额外的能量摄入以应对年度周期中的未来事件。因此，空间利用和移动模式可能会成为一种有效的策略，以在非繁殖季节维持能量获取与保存之间的平衡。然而，针对这一问题的研究仍然匮乏，尤其是在跨半球候鸟方面。
利用GPS追踪数据和最近开发的连续时间随机过程建模框架，我们分析了群居的长途迁徙滨鸟——哈德逊杓鹬（Limosa haemastica）非繁殖种群的精细尺度移动。具体而言，我们评估了这些极端迁徙者在南美洲南部的一个主要非繁殖地是否表现出受限、共享和周期性的空间利用模式。最后，通过广义相加模型，我们测试了观察到的模式在昼夜周期内是否一致。
总体而言，杓鹬表现出精细调整的范围居留和周期性移动（每24 - 72小时一次），昼夜之间相似。值得注意的是，范围居留个体在空间上分为三组。相比之下，一小部分杓鹬表现出不可预测和不规则的移动，增加了种群内的功能连通性。
在沿海非繁殖区，由于潮汐周期，资源可用性高度可预测，昼夜的范围居留策略是长途滨鸟种群的常见模式。一部分非居留杓鹬表现出的替代模式提供了功能连通性，并表明探索倾向可能对信息获取至关重要，且与个体特征相关。我们所采用的方法有助于阐明迁徙物种在非繁殖季节移动阶段的组成如何运作，并且也可以在非迁徙物种中复制。最后，我们的结果强调了将移动视为年度周期内连续统一体的重要性。
